From what I have read so far, it sounds like there is no problem with an owner getting their home week reservations? (Unlike Marriott points) I need summer weeks. And it sounds like Hilton is the easiest to get into Hawaii with points from other locations?
I will add some more details to what
@csodjd has said. With regards to HGVC, the terms that you are using (Home week reservations and get into HI with points from other locations) are two different things. A Home week reservation means that you own that specific location, room size and season. This will also be a 1-week reservation starting on whatever day the home week reservation starts for that resort (usually it will be Sat-Sat but not always as noted previously). You book your home week reservation at 12 and 9 months for most resorts (Hokulani Waikiki and Grand Islander are between 12 and 6 months).
If you are using points from another resort, then you will be booking during the club window (usually < 9 months but note that Hokulani Waikiki and Grand Islander are < 6 months). My observations are that the BI has much more availability than Oahu during club season. I think that Oahu is bookable but you will need to be more flexible. If you need specific date, room size, view and location then it might be best to purchase that for your home week.